When a chemical substance is incorporated into a solid material, a controlled release system is important in order to facilitate release of the chemical substance at a designated rate. Controlled release systems are particularly needed in the medical field where controlled drug delivery is required, and in various industrial applications where a controlled chemical release is required such as agricultural chemical applications, cosmetics, and catalysis.
Heretofore, various techniques and materials have been proposed for controlled release systems, but most are directed to mixing a chemical substance into a polymer gel or forming a complex consisting of a chemical substance and a polymeric material such as organic poly(lactic acid) or wholly inorganic material such as porous silica. Although silica gels are versatile and can incorporate various types of chemical substances therein, the release of substances from the silica matrix comprises a diffusion release mechanism and therefore rapidly decreases.
In recent years liquid solutions or coating films, which comprise surfactant molecules as the main component, have begun to emerge as promising controlled release materials. As a result of trends toward more complex controlled release materials with the proper release profile and safety, polymer surfactant molecules have been rigorously researched and have found use as controlled release agents.
However, many of the polymer coatings and formulations used in controlled release applications lack the ability to tune the release profile of the encapsulated molecular species. Further, the polymer erodes and the chemical substance is released into the environment. Also many controlled release formulations are liquid and therefore lose their ability to control the release of their contents upon dilution.
What is needed is a release device with release characteristics which can be easily tuned over a wide range.